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Contracting CAG/CTG repeats using the CRISPR-Cas9 nickase
Cinzia Cinesi1, Lorène Aeschbach1, Bin Yang1
1Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland.
Nature Communications
|November 10, 2016
Summary
Scientists discovered a new method to contract CAG/CTG repeats, which are linked to neurological diseases. This CRISPR-Cas9 nickase approach shows promise for developing treatments by reducing harmful repeat expansions in vivo.
Area of Science:
- Genetics
- Molecular Biology
- Neuroscience
Background:
- CAG/CTG repeat expansions are associated with over 13 incurable neurological diseases.
- Disease severity correlates with repeat tract length, suggesting repeat contraction as a therapeutic strategy.
Purpose of the Study:
- To investigate methods for specifically inducing CAG/CTG repeat contractions.
- To understand the mechanisms underlying repeat instability and contraction.
Main Methods:
- Utilized a GFP-based chromosomal reporter to monitor repeat expansions and contractions.
- Employed CRISPR-Cas9 D10A nickase to induce targeted DNA damage within repeat tracts.
- Investigated the roles of DNA damage response kinases (ATM, ATR) and repair proteins (MSH2, XPA).
Main Results:
- Inducing double-strand breaks caused instability in both expansion and contraction directions.
- CRISPR-Cas9 D10A nickase primarily induced contractions, independent of single-strand break repair.
- Nickase-induced contractions were dependent on the ATM kinase.
- ATR inhibition, in a MSH2- and XPA-dependent manner, increased both expansions and contractions.
Conclusions:
- DNA gaps within repeat tracts promote contractions.
- The type of DNA damage dictates the direction and extent of CAG/CTG repeat instability.
- This study provides a foundation for inducing CAG/CTG repeat contractions in vivo for therapeutic purposes.
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